Various types of medical devices employ a needle for piercing the skin of a patient for diagnostic or therapeutic purposes. One such device is a blood collection device which includes a needle for piercing a blood vessel of the patient to allow blood to be sampled from the patient. When the needle is inserted into the blood vessel of the patient, blood is withdrawn through the needle into a vacuum collection tube. Handling of such needle-bearing medical devices after the needle is withdrawn from the patient can result in transmission of various pathogens, most notably human immune virus (HIV), to uninfected medical personnel, due to an inadvertent prick.
Since the mid-1980s, concern over the risk of accidental needle stick injuries has spawned a number of design approaches for safety needle devices. Such devices can be broadly categorized as sliding sheath needle devices, wherein a physical barrier is positioned about the needle tip after use, and needle-retraction devices, wherein the tip of the needle is withdrawn into the device after use. The category of needle retraction devices can be further subdivided into manual and automatic retraction devices. Manual retraction devices, as exemplified by U.S. Pat. No. 4,026,287 to Haller, U.S. Pat. No. 4,592,744 to Jagger, U.S. Pat. No. 4,808,169 to Haber et al. and U.S. Pat. No. 5,067,490 to Haber, require the user to pull or slide a needle-engaging mechanism rearwardly for a sufficient distance to withdraw the needle into the device. In automatic needle retraction devices, a biasing member, such as a spring, is employed to withdraw the needle into the device in response to activation of some release mechanism on the part of the user. Such devices are exemplified by U.S. Pat. No. 4,813,426 to Haber et al. and U.S. Pat. No. 5,125,414 to Dysarz.
U.S. Pat. No. 4,747,831 assigned to Becton Dickinson and U.S. Pat. No. 4,900,307 to Kulli show respective automatic retractable-needle catheter stylets and syringes. The devices shown in the last-mentioned two patents are disclosed to be actuatable on the part of the user by applying a simple unitary motion that entails a simple single-stage movement in just one direction. Specifically, these latter patents show devices in which retraction is effected by depressing a single surface or member for a short distance in a single direction. Hence, during preparation for use of such devices, the user must be mindful not to prematurely trigger the needle retraction mechanism by accidentally contacting the surface for actuating the retraction mechanism. Because medical needle bearing devices are often employed under distracting circumstances, it would be desirable to provide an automatic needle retraction-mechanism in which a compound action or dual motion is required by the user in order to effect automatic retraction of the needle. Such a mechanism would desirably require the user to act upon more than one surface of the retraction mechanism to effect withdrawal of the needle into the device. It further would be desirable to require that such actions occur along different directional axes to further decrease the likelihood of undesired or accidental premature retraction of the needle.
Of the aforementioned prior art devices which have automatic retraction, all require a needle structure having an enlarged head, lip or rim extending radially outwardly from the axis of the needle to provide a block or enlarged surface on the needle which is biased toward retraction by the spring and which can be restrained against retraction by a latching mechanism. In such devices, failure of the latch mechanism can occur to cause premature retraction of the needle. Hence, it would be desirable to provide an automatic needle retraction mechanism in which the latch mechanism operates more directly upon the needle, rather than through a block or rim surface on the needle.
After use of a needle bearing medical device, a small volume of contaminated fluid or blood may remain inside the needle after it is withdrawn from the patient. Depending upon the gauge of the needle used with the device, such residual fluid or blood may be ejected from the forward end of the needle during the rearward acceleration experienced in retraction of the needle. Such forward fluid ejection can result from insufficient capillary adhesion to retain the residual fluid against inertial forces, or against the hydraulic force exerted upon the residual fluid by inrushing fluid or air during rearward acceleration in retracting the needle. It would further be desirable to provide a structure in an automatic needle retraction device that would prevent such ejection of residual blood or fluid from the forward end of the needle during retraction.